Op does NOT have a ‘lackluster’ GPA. This impression was caused by his/her attempts at 'translating ’ it. Op has a 4.0 in a curriculum that checks the ‘most rigorous ’ box in us terms and predicted results that place him/her in the top students nationally.
Also, Portuguese schools actively discourage EC’s since they distract from the all-important national exams so it’s good op has any, and has meaningful plans to expand the ones he has.
All in all, taking a gap year to strengthen his application with the better ec (which he can start working on now) and the national examinations results (which s/he’ll have in Summer 2017) is a good plan. As for what happens in 2023 after opt… Seriously OP is dreaming right now and likely can’t imagine the world and himself, how much tjeyl’'have changed, just like as a 5th grader s/he had no idea what s/he’d be like at 18.